The objective of this research project is to indicate a role for nonmuscle actin and myosin in the morphological changes that sperm undergo during maturation in the male reproductive tract and during capacitation in the female tract prior to fertilization. A role for nonmuscle actin and myosin will be investigated in 1) the migration of the cytoplasmic droplet down the sperm midpiece during maturation in the epididymus, 2) the structural maturation of the acrosome during epididymal transit, and 3) the fusion and vesiculation of the acrosome in capacitated sperm. Experiments will be done to identify actin in mammalian spermatozoa in different physiological stages by immunofluorescent labeling, followed by biochemical and structural characterization of the sperm actin. Sperm myosin will be identified by actin-stimulated adenosine triphosphate hydrolase activity and its ability to bind actin. The enzyme will be isolated and its intracellular location and structure will be studied. Experiments will be done to correlate actin-myosin structure and interaction with the cellular functions of spermatozoa. The experiments will include immunofluorescent labeling and biochemical analysis of protein structure and enzymatic activity.